Search

The genus Gambierdiscus is a complex and diverse group of marine dinoflagellates that produce a range of bioactive compounds, including ciguatoxins and maitotoxins. These toxins can accumulate in the food chain, leading to ciguatera poisoning in humans who consume contaminated fish. Recent research has highlighted the chemical diversity within the genus Gambierdiscus, with different strains producing distinct sets of toxins. This diversity presents challenges for the development of effective detection and management strategies for ciguatera, but also offers opportunities for the discovery of new bioactive compounds with potential applications in medicine and other fields. Understanding the chemical diversity of Gambierdiscus and its associated toxins is therefore an important area of research with implications for public health and biotechnology.

Gambierdiscus is a genus of benthic dinoflagellates that produce ciguatoxins (CTXs) and maitotoxins (MTXs), which are among the most potent marine toxins known. CTXs are bio-accumulated and biotransformed along the marine food chain and are involved in Ciguatera Fish Poisoning (CFP). Several species have recently been described, and CFP has recently been reported from non-endemic areas, namely the Canary Islands. Little is known about how toxicity varies among species and isolates of Gambierdiscus. This study examined the toxicity of 13 strains of Gambierdiscus, seven from the Pacific Ocean (G. pacificus CCMP 1650, G. sp. VGO 917, G. australes CCMP 1653, G. scabrosus KW070922_1, G. sp. Vietnam, G. caribaeus BILL HI Gam8, G. carpenteri PAT HI Jar7 Gam11), one from the Mediterranean Sea (G. carolinianus Greece Gam2), and five from the North-Eastern Atlantic Ocean (G. australes VGO 1178, G. australes VGO 1181, G. silvae VGO 1167, G. silvae VGO 1180, G. excentricus VGO 791). Algal cells were extracted with methanol, and extracts were partitioned between dichloromethane and aqueous methanol. The toxicity of pre-purified extracts has been evaluated using an ouabain/veratridine neuro-2a assay and a human erythrocyte lysis assay. In general terms, all strains showed hemolytic activity in the aqueous methanol fraction in the range of pgMTXeq/cell, and neuro-2a cytotoxicity in the dichloromethane fraction in the range offgP-CTX-3Ceq/cell. G.excentricus (Canary Islands) was an exception, with a neuro-2a cytotoxicity in the range of pgP-CTX-3Ceq/cell, in accordance with data previously reported by Fraga et al. (2011).

Ciguatera fish poisoning (CFP) is a food-borne illness caused by consumption of fishes contaminated with polyether toxins known as ciguatoxins (CTXs). Originally known as a tropical disease, CFP is being increasingly reported from areas previously not considered endemic. The benthic dinoflagellate Gambierdiscus is considered to be the primary producer of CTXs. This genus has recently been shown to have an increasing number of species, also discovered in areas where it had not been observed before.This genus also produces other types of potent toxins, such as maitotoxins and others. CTXs are bio-accumulated and transformed in herbivorous and carnivorous fish along the marine trophic chain. The study presented here is part of a PhD aiming at the elucidation of hitherto unidentified Ciguatoxins in recently discovered species from the Caribbean and North East Atlantic seas. Cultures have been obtained from culture collections and from international collaborators for evaluation of growth characteristics and toxin production. To date, a total of 19 strains are currently maintained in our laboratory, belonging to eleven different species from the Pacific, Caribbean and North East Atlantic areas. Extraction techniques were evaluated using an ultrasonic probe and a bead-mill. As the toxins of most of the strains are not yet known, extraction efficiency was evaluated using algal metabolites of similar nominal mass and chromatographic retention times as CTXs. These initial trials suggest that both techniques have very similar extraction efficiency. These trials also suggest that duplicate extraction of pellets is sufficient for retrieval of more than 95% of the metabolites in the molecular size range of CTXs. Different culture media (L1, L1+ soil extract, K2, K2 + soil extract, Kmodified and IMK2) were evaluated for their influence on growth of one species (CCMP 1653, a Hawaiian species). For this particular species, no significant major differences were detected in cell volumes; however, some differences were observed in cell densities. Further studies will focus on bioguided fractionation of toxic strains in combination with high resolution mass spectrometry to pinpoint previously undescribed compounds.

The scientific poster entitled "Complex Toxin Profile of French Mediterranean Ostreopsis cf. ovata Strains and Ovatoxins Prepurification" presented at the 16th International Conference on Harmful Algae (ICHA 2014) in Wellington, New Zealand, described the results of a study on the toxin profile of Ostreopsis cf. ovata strains found in the French Mediterranean region. The study was conducted by a team of researchers from various French institutions, including the French Research Institute for Exploitation of the Sea (Ifremer) and the Laboratoire d'Océanographie de Villefranche (LOV). The poster outlined the methods used for the extraction and purification of the toxins produced by Ostreopsis cf. ovata strains, and the subsequent identification and characterization of these toxins using various analytical techniques, including liquid chromatography and mass spectrometry. The study revealed a complex toxin profile of Ostreopsis cf. ovata strains, with the presence of several types of ovatoxins, including previously unreported variants. The results of the study have important implications for the monitoring and management of harmful algal blooms (HABs) caused by Ostreopsis cf. ovata in the French Mediterranean region and other parts of the world. The authors of the poster suggested that further studies are needed to fully understand the toxicity of these strains and the potential risks to human and animal health.